feat: Add dnsdist as backend

dnsdist.service

@@ -0,0 +1,48 @@
+[Unit]
+Description=DNS Loadbalancer
+Documentation=man:dnsdist(1)
+Documentation=https://dnsdist.org
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+ExecStartPre=/usr/bin/dnsdist --check-config
+# Note: when editing the ExecStart command, keep --supervised and --disable-syslog
+ExecStart=/usr/bin/dnsdist --supervised --disable-syslog
+User=root 
+Group=root
+Type=notify
+Restart=on-failure
+RestartSec=2
+TimeoutStopSec=5
+StartLimitInterval=0
+
+# Tuning
+LimitNOFILE=16384
+TasksMax=8192
+
+# Sandboxing
+CapabilityBoundingSet=CAP_NET_BIND_SERVICE
+AmbientCapabilities=CAP_NET_BIND_SERVICE
+LockPersonality=true
+NoNewPrivileges=true
+PrivateDevices=true
+PrivateTmp=true
+# Setting PrivateUsers=true prevents us from opening our sockets
+ProtectClock=true
+ProtectControlGroups=true
+ProtectHome=true
+ProtectHostname=true
+ProtectKernelLogs=true
+ProtectKernelModules=true
+ProtectKernelTunables=true
+ProtectSystem=full
+RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+RestrictNamespaces=true
+RestrictRealtime=true
+RestrictSUIDSGID=true
+SystemCallArchitectures=native
+SystemCallFilter=~ @clock @debug @module @mount @raw-io @reboot @swap @cpu-emulation @obsolete
+
+[Install]
+WantedBy=multi-user.target